Simplify the discovery script.

Ensure the script works also when the HUE_BRIDGE and HUE_KEY are not set. Since we're trying to discover the bridge IP we cannot set is before we run this script.
Added missing dependency.

The LWP::Protocol::https module depency was missing. If it is not installed the https GET request to www.meethue.com fails in the nupnp function.
Added minimal documentation in POD format, bumped version number to 0.5